BEETLES 349 



But the beetle is excelled by its olive-green larva in ferocity, though, 

 strange to say, the aperture of the mouth in this formidable creature is 

 very small and quite useless for the reception of food. Its place is 

 supplied by the powerful pincer-shaped mandibles, each of which is per- 

 forated by a canal. When the larva pierces the body of its victim with 

 these instruments, it injects through the canal a drop of a brownish saliva 

 which is poisonous, and kills the prey and also dissolves the soft parts 

 of its body. (Allow a larva to bite into a piece of meat.) The parts so 

 dissolved (i.e., digested outside of the body) are then sucked up, so that 

 nothing is left of the prey (in the case of an insect) but the empty 

 chitinous skeleton. The legs, as in the beetle, are furnished with 

 bristles. But locomotion is chiefly effected by undulatory movements 

 of the worm-shaped body. (Compare with ringed snake and eel.) For 

 the purpose of breathing, the larva elevates above the surface of the 

 water two long tubes situated at the end of the abdomen, and each 

 bearing a small plate covered with hair and proof against wet. All 

 other aquatic insect larvae also breathe by air-tubes ; for, inasmuch as 

 finally they develop into animals passing their life in the air, they 

 must be provided with respiratory organs adapted to an aerial existence. 

 (Compare larvae of dragon flies and May flies.) The larva finally burrows 

 its way into the earth outside of the water, and there passes into the 

 pupa stage. 



Allied Species. 



The small black beetles often seen gyrating in endless " figures of 8 " 

 on the surface of the water, suddenly diving down on the approach of 

 danger, but soon reappearing to continue their play, are known as 

 Whirligig Beetles (Gyrinus natator). They are adapted for these 

 peculiar movements by a broad, flattened body and their fin-like middle 

 and hind legs. The front-legs (prehensile legs), on the other hand, are 

 elongated and arm-like, and are used for seizing the prey, which consists 

 of all sorts of small water animals. The largest of all the water beetles 

 (reaching a length of about 1| inches) is the pitch-black Great Water 

 Beetle (Hydrophilus piceus). Its antennae are club-shaped. Though 

 its middle legs have the form of oars, this insect is not nearly as good a 

 swimmer as the common water beetle, its body being high, stout, and 

 provided with blunt edges. Hence its food consists chiefly of vegetable 

 substances. This beetle packs its eggs into a very neat-looking web, 

 which swims on the water like a small bladder provided with a chimney 

 for ventilation. The larvae are very similar in appearance to those of the 

 common water beetle, and of the same predaceous habits. 



